This one isn’t as much a tool as a process, but it’s a process that produces good, quick, measurable results.
Firefox is a cool browser, and has the best collection of add-ons available. One place where it falls down is that it can accumulate junk in its internal database. This causes slow startup, and just a general lethargy.
The great news is that it’s easy to clean up the database. And it works. One machine I did this on had the startup time cut in half. Not as measured on a stopwatch, but it went from “way too long” to “not too bad”.
The instructions are found at Dave Farquhar’s blog entry here. I’m going to let him explain it. Read the article and the two comments. Do it.
You’ll be happy.